asphalt pavement research trends€¦ · initial cost. future practice: focus on profit from...
TRANSCRIPT
Hussain U. Bahia & Carl M. Johnson University of Wisconsin‐Madison
2009 Annual WAPA Conference December 1‐2, 2009, Middleton, WI
Asphalt Pavement Research Trends
Current / Future Focus Areas •
Mechanistic Design –
AASHTO MEPDG
•
The Environment –
Energy, Emissions & Noise
•
Safety –
Friction and tire‐surface interaction
•
Superior Materials –
Modified Binders
–
Micro‐mechanics, Imaging & Visualization to learn
AASHTO MEPDG
Fully Integrated Design Software•Traffic•Environment•Structure •Mix Design •PG Grading•Pavement Distresses
Performance CriteriaDistress
Target
Distress
Predicted
Reliability
Predicted Acceptable
Terminal IRI (in/mi) 172 104.1 98.9 PassAC Bottom Up Cracking(Alligator Cracking) (%): 25 4.9 92.2 PassAC Thermal Fracture (Transverse Cracking) (ft/mi): 1000 74.8 99.9 PassPermanent Deformation‐
AC Only (AC Only) (in): 0.25 0.21 71.1 FailPermanent Deformation – All Layers(Total Pavement) (in): 0.75 0.65 81.6 Fail
Output Example ‐
PG 64‐22
Performance CriteriaDistress
Target
Distress
Predicted
Reliability
Predicted Acceptable
Terminal IRI (in/mi) 172 90 99.3 PassAC Bottom Up Cracking(Alligator Cracking) (%): 25 4.9 92.8 PassAC Thermal Fracture (Transverse Cracking) (ft/mi): 1000 74.8 99.9 PassPermanent Deformation‐
AC Only (AC Only) (in): 0.25 0.17 90.6 PassPermanent Deformation – All Layers(Total Pavement) (in): 0.75 0.61 92.2 Pass
Output Example ‐
PG 76‐22
The Environment (Sustainable Roads)
•
Asphalt is one of the most sustainable construction materials
•
The next few years will quantify this
for designers and specifiers of roads
–
Increased recycling by design
–
Reduce energy and emissions •
Warm mix practice
–
Quiet roads by design of surface texture
Distribution of Energy Consumption Asphalt Roads
Total Energy Consumed(%)
Material ExtractionManufacturingPlacement
91.7 %
1.8 % 6.7 %
Source: Image used courtesy of Payne & Dolan
Current Practice: Focus on materials’
initial costFuture Practice: Focus on profit from reduced energy and lower emissions
Evolving Estimation & Analysis Tools
•
Pavement Life‐cycle Assessment Test for Environment and Economic Effects (PaLATE)
•
Plant Diagnostic and Optimization Tool–
Pennsylvania Asphalt Pavement Association (PAPA)
•
Spreadsheet models for Energy and Emissions –
World Bank
–
Land Transport New Zealand
The Promise: Production Impact Less Energy + Less Impact on Environment
Source: FHWA
Fuel
/To
nEm
issio
ns/T
on
Models: Fuel Consumption Estimate how much energy you can save
0
0.5
1
1.5
2
2.5
100 150 200 250 300 350 400 450
Mix Temp (o
F)
Fuel
Con
sum
ptio
n (g
al /
ton
mix
)
0
50
100
150
200
250
300
350
400
3
5% Moisture
2% Moisture
O.25 Gallon Per 50 F
Opportunities for Asphalts
•
Design for superior safety
–
Selecting gradation to
control texture spectrum
–
Better water drainage
results in lower skid risk
and better visibility
–
Specific surface texture
can increase friction
•
Design for less noise
–
Dense graded but
selected texture
spectrum
–
Reduce noise generation
–
Increase noise
absorption
Asphalt – Drainable Surface Safety through better visibility and friction
Porous
Non-PorousSan Antonio Interstate Highway IH 35 before and after paving with Asphalt Rubber (RPA News, Vol 7, No.4, Spring 2004)
Macro‐texture/Laser Profilometer Work in collaboration ( University of Pisa)
WavelengthProfile
Ampl
itude
Length
•Device •Sampling Rate
•Sampling Interval
•Vertical Resolution
•Measuring Speed
•Length of Profile
•Stationary Profilometer •16 kHz •0.1 mm •0.05 mm •Manual •750 mm
•Mobile Profilometer •16 kHz •1 mm •0.05 mm •20 km/h •unlimited
Macrotexture Spectrum To Reduce Tire/Road Noise
•
Optimize
“Texture level”
to generate less noise
20
25
30
35
40
45
50
55
60
315
250
200
160
125
100
80.0
63.0
50.0
40.0
31.5
25.0
20.0
16.0
12.5
10.0
8.00
6.30
5.00
4.00
3.15
2.50
2.00
Lunghezza d'onda (mm)
Liv
ello
di T
essi
tura
(dB
rel
. 10
-6m
RM
S)
Texture Wavelength
(After Losa et al. 2009)
Noise Absorption Modeling Voids Structure (Losa et al. 2008/09)
DP
LP
LA
DA
PoreAperture
F = Microstructural Model
G = Theoretical Model
= F(DP, LP, DA, LA
)
(DP, LP, DA, LA
) = G(Composition Characteristics)
Micro‐texture (Friction) Measurements
• British Pendulum Skid Resistance Tester •
Friction measured by swinging the
pendulum.
•The loss of the kinetic energy as result of the interaction between the rubber and the sample surface is reported as the British Pendulum Number (BPN)
•Higher BPN values indicate higher surface microtexture and better skid resistance.
BPN – Friction Number As a function of Aggregate Gradation
R² = 0.7509
0
10
20
30
40
50
60
70
80
90
0 2 4 6 8 10
BPN
Gradation (Beta Index)
Visualization and Imaging UW‐
MSU Software 09
Will be proposed as an AASHTO Standard
(1) Image
processingprocessing
(2) Image
analysisanalysis
12
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
(1) Image processingprocessing(2) Image analysisanalysis
Contact pointsContact points
OrientationOrientation
SegregationSegregation
Software Updates of ’09 Detail of two part process
G1
G2
G3
Effect of Compaction Method – Initial Analysis
German Steel Sector
Superpave Gyratory
MarshallKneading Compactor
Compaction Method A
Kneading Compactor 126 2.78Marshall 125 2.76German Steel Sector 167 0.22Superpave Gyratory 90 5.54
: Indicates the predominant orientation angleA: represents the amplitude or severity of
deviation from uniform (zero=uniform)
FHWA‐UW ‐‐ X‐Ray CT Imaging
Hot Mix Asphalt LCPC Mix compacted to 35 gyrations (~4% air voids)
LCPC Mix compacted to 160 gyrations (~1.5% air voids)
Images from Kutay et al. 2008
Future Highways in The USA – Will be built with Less Impact on Environment
Low Energy, Low Emissions, and Low Noise Asphalt, can deliver these in the NEAR future
31
• ~ 4.0 Million Miles• ~ 2.2 million Paved• ~ 93 % Asphalt • ~30 million tons/Y
• ~ 4-5 million Modified Asphalts
X
Future Highways in The USA – Will be built with Less Impact on Environment
Low Energy, Low Emissions, and Low Noise Asphalt, can deliver these in the NEAR future
UWMARC.ORG
Concluding Remarks •
The next 10 years, many opportunities
•
Asphalt will not be the same , it will much improved and more function specific
–Opportunities for better role in pavement structure through
MEPDG
–Opportunities for lower cost and less impact on environment
–Less energy, less emissions, and less noise
–We will see more modified binders and mixtures